Remove duplicate provided identifiers
If I provide an identifier multiple times, it could be replaced with a single occurrence of the identifier. Thus,
(provide
a
b
a)
could be rewritten to just
(provide
a
b)
This seems doable. Does it need to catch duplication across multiple provide forms, or would duplication within a single provide form be enough? The latter is much easier to implement currently. Also, how common an issue is this in practice? Links to files/commits/pull requests where this rule would have helped would be great.
I guess it's pretty rare. I'm not drawing on experience with PRs or other high-quality code -- I'm reflecting on my own poor code!
Doing this for a single provide form would be a good (and easier) start.